import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int a, b, c, d, e;
        a = in.nextInt();
        b = in.nextInt();
        c = in.nextInt();
        d = in.nextInt();
        e = in.nextInt();
        RR rr = new RR();
        double dd = rr.fun(a, b, c, d, e);
        System.out.printf("%.2f", dd);
    }
}

class RR {
    public double fun(int a, int b, int c, int d, int e) {
        // 计算平均值
        return (a + b + c + d + e) / 5.0;
    }
}